Both the deaths have now been linked to an apparent 2012 plot to replace the leader with Kim Jong Nam, reported to have been hatched in the Chinese capital and the source of continuing tensions between Pyongyang and Beijing.

Image:Kim's executed uncle Jang Song Thaek was branded 'worse than a dog'

According to Japan's Nikkei Asian Review magazine, Jang met with China's then-president Hu Jintao in Beijing less than a year after Kim replaced his late father as North Korea's leader.

The publication claims Jang proposed toppling the young ruler, with Beijing's help, in favour of Kim's elder half-brother.

But he did not get a clear answer from the Chinese leader who was dealing with his own problems at home, the report states.

An ally of Kim within the Chinese government, Zhou Yongkang, later secretly informed him of the coup plot, on which the dictator is said to have flown into a rage.

Jang was executed in 2013 after being removed from all his posts over allegations of corruption, drug use, gambling, womanising and leading a "dissolute and depraved life".

State media branded him "worse than a dog", a "counter-revolutionary" and "despicable human scum".

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Image:Kim Jong Nam was killed by a nerve agent at Kuala Lumpur airport

However, a widely-published account of Jang being stripped naked and fed to a pack of starving dogs was later debunked.

The Nikkei Asian Review added Zhou was arrested at the same time as Jang's killing, but Beijing hid news of his detention until months later in order to hide a link between the pair's fate.

He was jailed for life in 2015 after state TV showed him pleading guilty to bribery, abuse of power and intentionally disclosing national secrets.

Earlier this year, Kim Jong Nam - who had been living in exile in the Chinese territory of Macau - died at Kuala Lumpur airport in Malaysia.

Video:N Korea defector on Kim's brutal regime

Two women have been charged with his murder after being accused of smearing his face with a nerve agent.

The US and South Korea accuse Pyongyang of being behind the killing, although the women claim they believed they were taking part in a reality show prank.

The reported coup plot has led Kim to "establish an intense mistrust" of China, according to the Nikkei Asian Review, with North Korea's ruler stepping up efforts to gain nuclear weapons as part of a plan for Pyongyang to break away from Beijing's influence.

Recent missile tests by North Korea have escalated tensions with the US, with Kim threatening to target the US Pacific island territory of Guam.